Chemical Vapor Deposition Growth of Degenerate p-Type Mo-Doped ReS2 Films and Their Homojunction.

Substitutional doping of transition metal dichalcogenide two-dimensional materials has proven to be effective in tuning their intrinsic properties, such as band gap, transport characteristics, and magnetism. In this study, we realized substitutional doping of monolayer rhenium disulfide (ReS2) with Mo via chemical vapor deposition. Scanning transmission electron microscopy demonstrated that Mo atoms are successfully doped into ReS2 by substitutionally replacing Re atoms in the lattice. Electrical measurements revealed the degenerate p-type semiconductor behavior of Mo-doped ReS2 field effect transistors, in agreement with density functional theory calculations. The p-n diode device based on a doped ReS2 and ReS2 homojunction exhibited gate-tunable current rectification behaviors, and the maximum rectification ratio could reach up to 150 at Vd = -2/+2 V. The successful synthesis of p-type ReS2 in this study could largely promote its application in novel electronic and optoelectronic devices.

Use of immuno-dominant epitope derived from genotype 4 as a diagnostic reagent for detecting the antibodies against Hepatitis E Virus.

BACKGROUND: Despite the genotype 4 has become the dominant cause of hepatitis E disease in China, none antigen derived from genotype 4 of hepatitis E virus (HEV) was used in current commercial anti-HEV immunoassay, and the serological reactivity of antigen derive from genotype 4 is not well-charactered. METHODS: We expressed and purified the 4 main immuno-dominant epitopes derived from genotype 1 and 4 including ORF2 (410-621aa) of genotype 4, ORF3 (47-114aa) of genotype 4, ORF2 (396-606aa) of genotype 1 and ORF3 (56-123aa) of genotype 4. RESULTS: The ORF2 of genotype 4 displayed good diagnostics performance according to ROC analysis using in-house panel, and the immunoassays based the ORF2 of genotype 4 was then developed to detect the anti-HEV IgG antibodies and evaluated further in 530 anti-HEV IgG positive specimens and 380 negative specimens. The sensitivity and the specificity is 98.1% (520/530) and 94.7% (360/380) for immunoassay based on ORF2 of genotype 4, 96.6% (512/530) and 92.6% (352/380) for commercial immunoassay based on genotype 1. It is noted that all of the positive samples will be detected by combing two assays together. The anti-HEV immunoassays based on genotype 4 are in accordance with Chinese anti-HEV national standard,and show an good agreement of 95.8% with commercial assay (kappa=0.913, P=0.014). CONCLUSIONS: The immunoassay based on ORF2G4 displays good performance, and combining assay based on genotype 1 together with genotype 4 will benefit the HEV diagnosis in large scale samples.

Evaluation of cross-reactive antibody response to HVR1 in chronic hepatitis C.

AIM: To evaluate the presence and cross-reactive antibodies against hypervariable region 1 (HVR1) in hepatitis C virus (HCV) infected patients and its relationship with the progression of the disease. METHODS: Sixteen representative HVR1 proteins selected from a unique set of 1600 natural sequences were used to semiquantitate the cross-reactivity of HVR1 antibodies in the sera of HCV patients. Fifty-five chronic HCV patients including 23 with asymptomatic mild hepatitis, 18 with chronic hepatitis and 16 with liver cirrhosis patients were studied. RESULTS: The degree of the cross-reactivity of anti-HVR1 antibodies in 23 patients with mild asymptomatic hepatitis was 3.09 ± 2.68, which was significantly lower than in those with chronic hepatitis (5.44 ± 3.93, P < 0.05) and liver cirrhosis (7.44 ± 3.90, P < 0.01). No correlation was observed between the broadness of the cross-reactivity anti-HVR1 antibodies and patient's age, infection time, serum alanine aminotransferase activity, or serum HCV-RNA concentration. It was the breath of cross-reactivity rather than the presence of anti-HVR1 antibody in HCV sera that was associated with the progression of liver disease. CONCLUSION: The broadly cross-reactive HVR1 antibodies generated in natural HCV patients can not neutralize the virus, which results in persistent infection in patients with chronic hepatitis.

Detection of hepatitis C virus core antigen for early diagnosis of hepatitis C virus infection in plasma donor in China.

AIM: To evaluate the efficacy of a new hepatitis C virus (HCV) core antigen assay developed in China. METHODS: After the determination of HCV infection, 49 serial samples were selected from 11 regular plasma donors in 5 different plasma stations. To compare the performance of HCV core antigen detection and HCV PCR, these samples were genotyped, and each specimen was analyzed by ELISA for the detection of HCV core antigen and by qualitative HCV PCR. RESULTS: Among all of the sequential samples, the original 13 specimens were HCV RNA-negative, and 36 samples were HCV RNA-positive. Twenty-seven samples (75%) were HCV core antigen-positive from these HCV RNA-positive specimens. Conversely, 27 samples (93.1%) were found HCV RNA-positive in HCV core antigen-positive samples. Intervals between HCV RNA and HCV core antigen-positive, as well as between HCV core antigen-positive and HCV antibody-positive were 36.0 and 32.8 d, respectively. CONCLUSION: This HCV core antigen assay, developed in China, is able to detect much of anti-HCV-negative, HCV RNA-positive preseroconversion window period (PWP) plasma donations.

[Preparation of recombinant IL-1 fusion protein as the substrate for HCV NS3 serine protease].

AIM: To prepare recombinant IL-1 fusion protein as the substrate for the HCV NS3 serine protease. METHODS: NS5A-B gene fragment (2,412-2,427aa) synthesized by PCR was subcloned into prokaryotic expression vector pBVIL1 to fuse with IL-1 gene and the recombinant vector pBVIL1/NS5A-B was transformed into E.coli strain HB101. The fused protein was induced to express at 42degreesCelsius and purified by two-step column chromatography. The proteolysis of the purified IL-1 fusion protein catalyzed by NS3 serine protease was analyzed with SDS-PAGE, Western blot and ELISA. RESULTS: NS5A-B fragment gene was correctly subcloned into pBVIL1 vector and the fusion protein was expressed as inclusion body in transformed HB101 cells. The recombinant fusion protein can be cleaved into smaller fragments by NS3 protease. CONCLUSION: The recombinant fusion protein can be cleaved by NS3 serine protease successfully and specifically, suggesting that it can be used as a surrogate substrate of NS3 serine protease in searching for inhibitors of this protease.

Cloning, expression, and purification of HLA-A2-BSP and beta-2m in Escherichia coli.

Tetramer analysis is a novel technique in immunological research that has dramatically changed our knowledge of the immune response to pathogens, tumors and autoimmune disease. Through the formation of major histocompatibility complex (MHC)-peptide tetrameric complexes, it can provide accurate counts of antigen-specific T-cells and it allows their phenotypical and functional analysis. The tetramer is composed of the human leukocyte antigen (HLA) heavy chain, beta-2 microglobulin (beta-2m), the nominal peptide, and streptavidin. The HLA heavy chain and the beta-2m are expressed in Escherichia coli. But up to now, all laboratories have been expressing these two proteins by using isopropyl beta-d-thiogalactopyranoside IPTG. IPTG is very expensive, and it is tedious and laborious to induce expression protein. So it is difficult to scale up to express the objective protein. To address this problem, extracellular fractions of HLA-A0201 and beta-2m (absent signal peptide) genes were cloned from peripheral blood mononuclear cells (PBMCs) by RT-PCR. DNA coding for a Gly-Ser linker and a BSP (15-amino acid substrate peptide for BirA-dependent biotinylation) was added to the COOH-terminus of the extracellular fraction of HLA-A0201 by PCR, using an HLA-A0201 as the template. Then the HLA-A0201-BSP and beta-2m genes were cloned into pBV220 vector and expressed, respectively. The expressed proteins were purified and detected by ELISA and Western blot analyses. High-efficient expressions of HLA-A0201-BSP and beta-2m proteins lay a good foundation for further expression and purification in prokaryotic system and constructing MHC class I-peptide tetramer complexes to study the function of CTLs.

[Studies on the correlation between titer of antibodies against different function regions of hepatitis C virus and HCV RNA of chronic patients].

OBJECTIVE: To detect humoral immune response against different function regions of hepatitis C virus (HCV) in chronic patients, and further to investigate the correlativity between anti-HCV antibody titers and HCV RNA concentration. METHODS: Using recombinant dominate epitope antigens, e.g. HCV Core, NS3, NS4, NS5 and chimeric HVR1, a set of ELISA test reagents was formulated. Then, titers of antibodies against HCV different regions and the RNA concentration of HCV in chronic patient sera were detected by ELISA and quantitative RT-PCR technique, respectively. RESULTS: Great differences have been noted in antibody titers and positive rate of different HCV function regions in chronic patients. Antibodies against HCV Core and HVR1 have the highest positive rate, then NS3, NS4, and NS5 in sequence. CONCLUSION: The titer of antibodies against different regions of HCV in chronic patients has good correlation with HCV RNA concentration.

Cross-reactivity of hypervariable region 1 chimera of hepatitis C virus.

AIM: To analyze the amino acid sequences of hypervariable region 1 (HVR1) of HCV isolates in China and to construct a combinatorial chimeric HVR1 protein having a very broad high cross-reactivity. METHODS: All of the published HVR1 sequences from China were collected and processed with a computer program. Several representative HVR1's sequences were formulated based on a consensus profile and homology within certain subdivision. A few reported HVR1 mimotope sequences were also included for a broader representation. All of them were cloned and expressed in E.coli. The cross-reactivity of the purified recombinant HVR1 antigens was tested by ELISA with a panel of sera from HCV infected patients in China. Some of them were further ligated together to form a combinatorial HVR1 chimera. RESULTS: Altogether 12 HVR1(s) were selected and expressed in E.coli and purified to homogeneity. All of these purified antigens showed some cross-reactivity with sera in a 27 HCV positive panel. Recombinant HVR1s of No. 1, 2, 4, and 8# showing broad cross-reactivities and complementarity with each other, were selected for the ligation elements. The chimera containing these 4 HVR1s was highly expressed in E.coli. The purified chimeric antigen could react not only with all the HCV antibody positive sera in the panel but also with 90/91 sera of HCV -infected patients. CONCLUSION: The chimeric antigen was shown to have a broad cross-reactivity. It may be helpful for solving the problem caused by high variability of HCV, and in the efforts for a novel vaccine against the virus.